Dave's method of using the copper reducer/couplings works great, but I use
the standard chassis mount UHF connectors. The shield end of the reducer can
be slit, and then slid back out of the way while soldering the center
conductor. Then slide the reducers back down to the back of the UHF
connector and soldered. The rim on the back of the UHF conectors will keep
the reducer well centered. Probably not too good for UHF/uW but fine for HF.

The half inch compression fitting is fairly close fit to the PL259
barrel. Not exact but close. Just take your coax connector into
Lowe's or Home Depot...or your local hardware store and you'll find
some that fit.

yeah, i've had lots of fun with hardware store clerks... they want to help
but just can't understand why my pipe is full of foam and what that
strange silver plated fitting i want to put on it is.

another way to do it if you want a female connection on the cable is to
get a 1/2" copper coupling, take the center out of a barrel connector and
solder the shel into one side of the coupling, then hacksaw a slit in the
other end, solder the center pin onto the center conductor and put the
coupling on the hardline... secure with hoseclamp. you can use adapters
to step down to 1/2" for larger hardline up to about 1", just solder some
braid on the center conductor to step down to the center pin on the
barrel.